Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.
Etch processes may be referred to as wet or dry based on the phase of the etchants used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform patterned features. Dry etches are preferred when suitable chemistries are available and known. Dry etch chemistries can penetrate more constrained trenches and exhibit less deformation of delicate structures. However, dry etches are sometimes unavailable or at least unknown for a specific pair of materials.
Thus, there is a need for improved systems and methods that can be used to selectively remove an ever-increasing suite of materials with respect to other materials which may be present on patterned substrate in novel process flows.